BRIEF OHNE UMSCHLAG Hertwig, Richard Author: Hertwig, Richard Recipient: Haeckel, Ernst Dating: 04.06.1899
BRIEF OHNE UMSCHLAG Hertwig, Richard Author: Hertwig, Richard Recipient: Haeckel, Ernst Dating: 12.11.1899
BRIEF OHNE UMSCHLAG Hertwig, Richard Author: Hertwig, Richard Recipient: Haeckel, Ernst Dating: 21.11.1899